Tuning mechanism



Aug. 19, 1941. H, J, TYZZER 2,253,484

TUNING MECHANISM Filed April 19, 1940 27 la" '3m '84 INVENTOR.

Y /lguararjlezx 2%.51 M i i Patented Aug. 19, 1941 TUNING MECHANISM Howard J. Tyzzcr, Cincinnati, Ohio, assignor to The Crosley Corporation, Cincinnati, Ohio, a

corporation of Ohio Application April 19, 1940, Serial No. 330,588

(Cl. Z50-40) 2 Claims.

denser gang to a predetermined and pretuned position. Electrical means although they are easy to operate and smooth working are somewhat more subject to failure than are mechanical means and they are quite expensive of `manufacture. Mechanical means, on the other hand, though more certain of operation and susceptible to simple and economical manufacture are usually more diicult to operate. This is, they require more force to be exerted by the operator. For instance, a mechanically operated push button mechanism is harder to push than a similar device arranged for electrical operation and Where the member moved by the button or its associated structure is at a considerable angle to the latter the button is often hard to start. Once started, the cooperating elements move fairly easily to their limit of movement but as the initial push cannot Very well be quickly retarded the result is that the moving parts accelerate rapidly until they come to a sudden stop which produces a jolt. Thus, the force required to start the button yis too great at the intermediate and end parts of the stroke and this tends toward unsatisfactory and jerky operation.

One :of the reasons why a mechanical device of the nature described requires more force to operate is that the mechanical load thereon must be moved by the force exerted by the operator, whereas in the case of an electrical tuner the load is moved fby an electric motor or solenoid and the operator merely has to exert sufficient force to close a switch in order to apply the power of such motor or solenoid. Y

. Heretofore it has been customary to provide in conjunction with the automatic controls or preselectors, whether electrical or mechanical, a hand-operated tuning means by which stations intermediate those for which the automatic tuning device is set may be manually tuned by observing the pointer on a dial and by listening for the undistorted maximum signal. The manual tuning control which is usually mounted upon 'a shaft is connected to a visual indicator and to the same condenser gang as that used for automatic tuning, through shafts, gears, belts or pulleys, and the manual control, as well as the connecting members must all be moved on actuation of any one of the number of push buttons with which the receiver is equipped.

Such adjuncts to the automatic control have been a handicap to the construction of a smoothworking, easy-operating mechanism by reason of the additional load they place on the latter. It has not been possible to eliminate the manual tuning control and its connections without restricting the effective range of the set to those frequencies for which the push button controls are adjusted, nor can the indicator, which with its operating parts forms a considerable part of the load, be eliminated for it is essential when using hand tuning that the user have a visual indicator of the frequency or wave length to which he is tuned. If the indicator were disconnected from the manual tuning mechanism during thek time that the set is under automatic operation, then upon return to manual tuning there would. be no way of knowing that the indicator'was properly reconnected in order accurately to show the frequency -at which the set was tuned. The provision of means for disconnecting the indicator together with the manual tuning mechanism together with means for properly reconnecting them requires complicated constructions which are not commercially feasible.

Ihave devised a construction which solves these problems of mechanical tuning and which permits the same to be accomplished in a smooth, easy and uniform manner. The load of a separate hand-tuning knob and its connections with an indicator is eliminated, yet these adjuncts are readily'at hand for use if desiredl I have provided a tuning device which is simple of construction, easy of manufacture and which performs its intended function with the same smoothness, rapidity and uniformity las the more -complicated and expensive electrically operated ing description of a specific embodiment when read in conjunction with the accompanying drawing, in which Figure 1 is a fragmentary plan View, with parts broken away, of the chassis of a radio receiver in which the principles of the invention have been embodied.

Figure 2 is a front elevation of the structure shown in Fig. 1.

Figure 3 is a transverse section taken along line 3-3 of Fig. 2.

Figures 4, 5, 6 and '7 are perspective views of certain parts used in the construction of the automatic control.

Figure 8 is a wiring diagram of a tuned radio frequency receiver, illustrative of those in which the controls of the invention may be incorporated.

Briefly described, the invention may comprise the provision in a radio receiver of a pair of gang condensers each independent of the other and each having substantially the same range of capacity, together with means for optionally connecting one of said gangs in circuit for tuning the set to resonance throughout a given frequency range. One of said gangs is operable by the usual hand selector or knob and its shaft is connected by suitable means such as a belt and pulleys to a visual indicator, so that when such gang is in circuit the set may be tuned by hand by correlating the position of the indicator, which may consist of a pointer and a dial, with the sound emanating from the loud speaker or other sound reproducer. The means for optionally connecting one of the condenser gangs in circuit may comprise a switch by which the operator can throw out the first mentioned gang and simultaneously throw in a second gang so that the second gang is properly connected in circuit. In the embodiment described, this second gang is adapted and arranged to be operated by one or more of a plurality of push button controls and has no mechanical load thereon other than that required to connect the same for operation by the plunger or other member actuated by the push buttons and rotate the gang condenser. Thus the automatic control is relieved from the load of the manual tuning device and its connections with the indicator and the actuating members thereof may be quickly and easily operated by a very light touch.

In order to utilize the principles of the invention to best advantage it is desirable to use a pair of relatively small gang condensers mounted and balanced in such a way that the rotors thereof may be turned with the minimum of force. The invention contemplates means whereby each of the operating controls for automatic tuning locks to fix the position of the tuning condenser at the limit of its stroke. This feature obviates the necessity of providing any friction or drag on the condenser shaft and tends toward smooth, easy and uniform rotation thereof by the positioning mechanism.

Coming now to a more detailed description of the exemplary embodiment of the invention shown in the drawing, the automatic control may be contained within the casing 9 mounted on the chassis I of the receiver. It may consist of a plurality of push buttons II mounted on shaft I2 which has a reduced inner end portion |2a, connected with a plunger and rocker mechanism hereinafter more particularly described, by which the capacity of the condensers A and B of one gang can be adjusted. Actuation of any one of the push buttons II will through the connecting mechanism cause the rotors 36 of the condensers A and B to assume a position at which the capacity of the condensers is such that they tune the circuits within which they are contained, to resonance at a predetermined frequency. Condensers C and D of another gang are operable through shaft 12 and knob 1I so that when such gang is connected in circuit the same likewise may tune the same to resonance at any one of a number of frequencies within the range of the receiver. A pointer 83 may be slidably arranged to move along scale 84 to indicate the frequency at which the set is tuned on rotation of knob 'I I. A switch 93 operable by shaft 92 to which an actuating knob 9| is attached is provided so that either the gang A, B, used for automatic controly or C, D used for manual control with frequency indication, may be connected in circuit.

Referring now to the automatic tuning mechanism, the end portion Iia of the shaft I2 is reduced in order to provide a shoulder |2cZ against which is seated an upturned ear I3a of a plunger I3 which latter is disposed parallel to the shaft Ia. The ear |3a is secured against the shoulder |2d by a collar 29. The shaft |2a is threaded at one end with right-hand threads |2b and at the other end with left-hand threads I2C, cooperating respectively with complementary threads in the upturned ears I'la and 18a of members I1 and IB. These members contain slots I'Ib and |32) and are slidably secured to the plunger I3 by rivets I9, each having a shaft 20 extending through the slots, and a reduced end portion 2| adapted to be secured to plunger I3 as by insertion in apertures 22 in the plunger and expanded therein by swaging. The plunger I3 with its connected shaft I2 is arranged to reciprocate through guides formed by slots I4 and I5 at the front and rear of the casing 9 and as the plunger slides Within its guides it moves the members I 'I and I8. These are themselves adjustable by means of the screw threads just mentioned so that by turning the shaft I2 by the button I| their relative position with respect to the plunger I3 may be varied.

Depending from the plunger I3 is a projection I3b by means of which the plunger structure is normally held outward by a spring 23 connected between said projection and a portion of the casing 9, as shown in Fig. 3.

The limiting release position of the plunger may be governed by an upstanding portion I 3c on the end thereof which portion abuts against a bracket 89 secured to the rear wall of casing 9. Bracket 89 acts as a stop when the plunger is carried all the way out by reason of the force of the spring 23.

Each member I1 and I8 has a cam portion I`Ic and adapted on depression of the plunger to coact with the outer faces of a rocker plate 30 which is cut out centrally in order to receive the intermediate portion of each plunger mechanism. The rocker 39 may be pvoted at 3| on screws threaded into the sides of the casing and has secured thereto an arm 32, the end of which carries a gear segment 33 which cooperates with a pair of pinions 34 secured to shaft 35. The pinions 34 are spring pressed in relation to one another in order to obviate lost motion, as is well known in the art. Shaft 35 is mounted in a bracket 3l and carries the rotors 36 of the variable condensers A and B of the automatic tuning gang. The stators 33 of the gang are mounted on cross-members 39 in turn supported by members 40 of suitable insulating material. Members 40 are secured to the base 4I of bracket 31 which brackety may be secured to the lower side ofthe casing 9 as indicated in Fig. 3,'or it may be se- Vcured'directly to the bottom face of casing 9.

It will be readily perceived that actuation of any plunger through its associated push button causes cams |1c and Hic, whose relationship has been pre-adjusted, to position plate and to rotate shaft to a position which has been predetermined as that required to tune a given station.

The gears 33 and 34 may conveniently be re-Y latedvso that angular movement of the rocker 30 about its pivots 3| may be multiplied three or even four times when transmitted to the condenser shaft.

It will be understood that it is necessaryy to balance the gear ratio with the force required to move the rocker, that is, the greater the ratio the greater the force required. Consequently it is desirable not to use too high a ratio as it is irnportant that the force required to turn shaft 35 be reduced to a minimum.

As indicated in Fig. 3, connection may be made to stator 38 through one of the lugs 42. Similar connections may be provided for the stators of the other condensers. It will be understood that the rotors of the condensers are connected to chassis in the usual manner.

In Fig. l, one of the plunger mechanisms is shown fully depressed while the remaining ones are in their extended position. The section of .t

Fig. 3 shows this one plunger in its depressed position and by an examination thereof in conjunction with Fig. 1 it will be seen that each plunger is retained in depressed position by a plate 24 mounted on brackets 25 pivoted at 26 to a part of the frame 9. A spring 21 urges this bracket downwardly. The end of the plunger I3 is provided with a projection |3c and a V-shaped slot I3d. The result of this construction is that when the plunger is pushed to its innermost position, as shown in Fig. 3, the plate 24 snaps over projection |3c into the slot i3d thereby retaining the plunger against being returned to out position under the tension of the spring 23. Simultaneously the condenser shaft 35 is locked in position, which according to the setting of cams |1c and |8c, is such that a predetermined broadcasting station is tuned in. The plate 24 is provided with a rib 28. When an adjacent plungei is depressed its projection |30 engages the bottom of rib 28 and raises the plate 24 against the pressure of spring 21. This causes the plate to ride out of the slot i3d of the already depressed member which latter is withdrawn under the pressure of spring 23 to its outermost position and the slot |3d of the newly depressed plunger assumes a position in which the plate 24 slips thereon under the pressure of spring 21 and locks the mechanism at another pre-tuned position.

Thus, operation of any plunger mechanism will release a previously depressed plunger. This is advantageous in that each plunger is designed to tune in a predetermined station, the name of which is customarily marked on the face of the plunger, and by an examination of the controls the operator can readily perceive which plunger has been depressed and to which station the receiver is tuned.

As the capacity of the condensers A and B of the gang moved by the automatic mechanism above described is varied by rotating plate 30 and thus turning shaft 35, there is a minimum load to be moved on actuation of any one of the plunging members. The condenser shaft 35 is not interconnected in'any way to the manual tuning condensersC and D of the other gang, to their common shaft 12, or to the belts, pulleys andshafts connecting same to their indicator 83. All the parts of the manual tuning mechanism remain stationary land are unaffected by any movement ofany of the plungers I3.

-' The manual tuner consists of a pair of condensers C and D the rotors of which are mounted on shaft 12 for rotation in brackets 13. The rotors 14 'are secured to the shaft 12 in the usual manner and the stators 15 are mounted in a manner similar to those described in connection with the condensers A and B. In order to provide a visual indicator of the condition of tuning when the manual control is used, a sheave 16 is mounted on shaft 12 and connected as by a belt 11 running over pulleys 18, 19, v80 to a slider 8| which may be clamped to the belt and arranged to slide on the top edge of support 88. The slider 8| may carry a pointer 83 extending downwardly adjacent scale 84. In the embodiment shown, the scale is calibrated through the frequency range of the broadcast band and is disposed at the rear of a transparent Window 86 which is mounted in brackets 81, the parts being arranged so that a space is left for the reception of the pointer 83. The entire structure is supported by legs 88a for support 88 secured to the chassis as indicated in Figure 3. From an examination of the structure above described it will be apparent that rotation of knob 1| will tune the gang C, D and at the same time cause the indicator 83 to assume a position relative to the scale 84 such that the frequency atWhich the circuits of the set are tuned by varying the capacity of the condensers will be indicated.

In Figure 8 I have shown a fragmentary diagram of a tuned radio frequency circuit in which the structure of the invention may be utilized. It will of course be understood that the invention may be utilized in other circuits such as a superhetercdyne, by incorporating suitable condensers in the mixer input circuit and the oscillator circuit. In the circuit shown in Fig. 8 the radio frequency circuit including the inductance of the antenna coil secondary 94 is tuned by one or the other of condensers A and C. The output of the radio frequency amplifier 95 is coupled by transformer 96 to the detector tube (not shown). The secondary of the transformer 96 is tuned by one or the other of condensers B and D. Switch 93 is arranged as indicated in Fig. 8 so that either the gang A and B or C and D may be included in the respective circuits. Actuation of shaft 92 by knob 9| moves the switch to a position in which either A and B or C and D are connected in circuit. As both gangs have substantially the same range of capacity, either gang will tune the circuits in which it is incorporated in precisely the same manner. In Fig. 8 I have shown the rotors 36, 14 of the condensers connected to ground and the stators 38, 15 connected in circuit by leads 42, 42a, 4217 and 42e.

It will be understood that the invention is not limited to the use of a pair of gang condensers as described in the illustrative embodiment, but that pairs of three or four gang units may be used, each condenser designed to tune a given circuit.

Having thus described my invention, I claim:

l. In a radio receiver, in combination, an automatic tuner of the type wherein selected manually actuable members mechanically rotate a tuning condenser, said tuner comprising a condenser shaft and a series of actuable members each adapted and arranged to be actuated to rotate said shaft automatically to preselected positions upon actuation of one of said members, a condenser gang on said shaft comprising at least two variable condensers connected in the tunable circuits of said receiver; a manual tuning mechanism comprising a second condenser shaft, a member which may be actuated to rotate said second shaft manually to a desired position, a second condenser gang operatively connected to said second shaft comprising variable condensers in number and range identical with the rst condensers, a switch for optionally including said second condenser gang in said circuits in place of said rst condensers and a tuning indicator operatively connected with said manual tuning mechanism only.

2. In a radio receiver, in combination, a pair of fixed circuit elements, two pairs of variable tuning elements, separate actuating means connected thereto, each pair of variable tuning elements being adapted and arranged independently to tune circuits including said xed elements over a selected frequency range, the actuating means for one of said pairs adapted and arranged to move said pair automatically to any one of a number of predetermined positions within said range and actuating means for the other pair being adapted and arranged to move said pair manually to any position over the entire range, a tuning indicator connected to said last mentioned pair only and switching means for selecting either automatic or manual tuning.

HOWARD J. TYZZER. 

